Lead-free and antimony-free brass alloy

ABSTRACT

A lead-free and antimony-free brass alloy contains 56 to 66% Cu, 0.1 to 1.5% Mg, less than 0.1% Pb, and a balance of Zn. Unavoidable impurities are also present. According to other embodiments, different amounts of As, P, Al, Sn, Cu, Mg, Pb, In and Zn may be provided as well.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority, under 35 U.S.C. § 119, of German Patent Application DE 10 2021 119 474.1, filed Jul. 27, 2021; the prior application is herewith incorporated by reference in its entirety.

FIELD AND BACKGROUND OF THE INVENTION

The invention relates to a lead-free and antimony-free brass alloy.

In the past, the machinability of brass alloys has been improved by adding Pb in an extent of up to 4 wt%. However, adding Pb is no longer allowable, due to legal stipulations.

It has been found that the adding of Pb can be replaced by an addition of Bi. It has emerged, however, that the addition of Bi leads to hot embrittlement of the brass alloy. Brass alloys of that kind have only limited capacity for hot forming. Brass alloys of those kinds, consequently, are not used for compression-molded parts.

European Patent EP 3 320 122 B1 discloses a brass alloy admixed with neither Pb nor Bi. For improving machinability, it is proposed that 0.005 to 1.0 wt% In be added to the brass alloy. While the proposed addition of In does improve the machinability, machining is nevertheless accompanied by formation of relatively long spiral chips, which can lead to blockages as they are transported away, and to tool breakage.

European Patent Application EP 2 913 415 A1, corresponding to U.S. Pat. Application Publication No. 2016/0362767, discloses a further lead-free and bismuth-free brass alloy which, moreover, contains no Si. The known alloy contains 60 to 65 wt% Cu and also 0.01 to 0.15 wt% Sb.

The addition of Sb causes hot embrittlement. Alternatively, proposed in European Patent Application EP 2 913 415 A1, corresponding to U.S. Pat. Application Publication No. 2016/0362767, is an addition of 0.005 to 0.3 wt% P. The proposed addition of P makes processing by continuous casting more difficult.

European Patent EP 2 467 507 B1, corresponding to U.S. Pat. Application Publication No. 2012/0207642, discloses a lead-free brass alloy which contains Fe, Ni and Sn.

European Patent EP 2 133 437 B1, corresponding to U.S. Pat. No. 8,425,697 and U.S. Pat. Application Publication Nos. 2010/0080731, 2009/0311127 and 2009/0311130, discloses a lead-free free-cutting brass alloy which contains 0.6 to 2.5 wt% Mg and also 0.15 to 0.4 wt% P. The addition of P makes processing by continuous casting more difficult.

SUMMARY OF THE INVENTION

It is accordingly an object of the invention to provide a lead-free and antimony-free brass alloy, which overcomes and eliminates the hereinafore-mentioned disadvantages of the heretofore-known alloys of this general type and which has improved machinability. According to a further object of the invention, the brass alloy is to exhibit little hot embrittlement, allowing it to be processed by hot forming.

With the foregoing and other objects in view there is provided, in accordance with the invention, a lead-free and antimony-free brass alloy containing:

-   56 to 66% Cu, -   to 1.5% Mg, -   less than 0.1% Pb, -   a balance of Zn, and -   unavoidable impurities.

Suitable embodiments are apparent from the features of the dependent claims.

For the purposes of the present invention, [%] is understood to be per cent by weight.

It has surprisingly emerged that through the addition of 0.1 to 1.5% Mg as proposed in the invention, the Pb content can be established at less than 0.1% without undesirable formation of long spiral chips during machining. The proposed brass alloy is notable not only for improved chip breaking but also for little hot embrittlement. It may be processed by hot forming.

According to the invention a “lead-free and antimony-free brass alloy” is understood to be an alloy which contains less than 0.1% Pb and less than 0.001% Sb.

According to one advantageous embodiment, the alloy may contain less than 0.15% As and/or less than 0.15% P and/or less than 0.1% Al and/or less than 0.1% Sn. Sn stabilizes the β solid solution. As leads to improved corrosion resistance of the alloy, with As in particular counteracting removal of zinc. The addition of P improves the machinability of the alloy.

According to another advantageous embodiment, from 57 to less than 60%, preferably from 57.5 to 58.5% of Cu is present. The proposed alloy is more cost-efficient because of the relatively lower Cu contents.

According to another embodiment there is more than 0.5% Mg. The proposed Mg content contributes to improved machinability.

The Pb content is suitably in the range from 0.05 to 0.09%. The In content is less than 0.005%.

Lastly, according to one advantageous embodiment, it is proposed that the Zn content be 40 to 42.5%. An alloy having the proposed Zn content displays good machining properties.

The proposed lead-free and antimony-free brass alloy additionally enables good processing qualities in the continuous casting process.

Other features which are considered as characteristic for the invention are set forth in the appended claims.

Although the invention is illustrated and described herein as embodied in a lead-free and antimony-free brass alloy, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows a chip depiction after longitudinal turning of a first example alloy;

FIG. 2 shows a chip depiction after longitudinal turning of a second example alloy;

FIG. 3 shows a chip depiction after longitudinal turning of a third example alloy; and

FIG. 4 shows a chip depiction after longitudinal turning of a fourth example alloy.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIGS. 1-4 of the drawings in detail, there are seen chip depictions which were produced in each case by subjecting alloys to longitudinal turning at a rotary speed of 850 rpm. An indexable cutting insert was used with the identification KNMX160405 R8lC907. The scale bar included in FIGS. 1 to 4 is 5 mm in each case.

FIG. 1 shows a chip depiction after longitudinal turning of a first example alloy. The first example alloy is a reference alloy. The first example alloy contains 58% Cu and 42% Zn, meaning that the first example alloy contains no addition of Mg.

As can be seen from FIG. 1 , the longitudinal turning of the example alloy 1 produces long spiral chips. Such spiral chips are unwanted when machining. They may lead to blockages when being transported away, and to tool breakage.

FIG. 2 shows a chip depiction after the longitudinal turning of a second example alloy. The second example alloy contains 58% Cu, 41.5% Zn and 0.5% Mg. It is apparent that the chips generated during longitudinal turning are shorter than the chips shown in FIG. 1 .

FIG. 3 shows a chip depiction after the longitudinal turning of a third example alloy. The third example alloy is formed of 58% Cu, 41% Zn and 1% Mg. It is clearly apparent that the chips produced are again shorter than the chips generated by the longitudinal turning of the second example alloy.

FIG. 4 shows a chip depiction after the longitudinal turning of a fourth example alloy. The fourth example alloy is formed of 58% Cu, 40.5% Zn and 1.5% Mg. The chips generated during turning of the fourth example alloy are again smaller than the chips generated by the longitudinal turning of the third example alloy.

Therefore, through the proposed addition of 0.1 to 1.5% Mg to a lead-free and antimony-free brass alloy, considerably improved chip breaking can be achieved. The proposed brass alloy is notable, moreover, for little hot embrittlement. It may be processed by hot forming, particularly in a continuous casting process. 

1. A lead-free and antimony-free brass alloy, comprising: 56 to 66% Cu; 0.1 to 1.5% Mg; less than 0.1% Pb; a balance of Zn; and unavoidable impurities.
 2. The lead-free and antimony-free brass alloy according to claim 1, which further comprises less than 0.15% As.
 3. The lead-free and antimony-free brass alloy according to claim 1, which further comprises less than 0.15% P.
 4. The lead-free and antimony-free brass alloy according to claim 1, which further comprises less than 0.1% Al.
 5. The lead-free and antimony-free brass alloy according to claim 1, which further comprises less than 0.1% Sn.
 6. The lead-free and antimony-free brass alloy according to claim 1, which further comprises from 57% to less than 60% Cu.
 7. The lead-free and antimony-free brass alloy according to claim 1, which further comprises from 57.5 to 58.5% Cu.
 8. The lead-free and antimony-free brass alloy according to claim 1, which further comprises more than 0.5% Mg.
 9. The lead-free and antimony-free brass alloy according to claim 1, which further comprises from 0.05% to 0.09% Pb.
 10. The lead-free and antimony-free brass alloy according to claim 1, which further comprises less than 0.005% In.
 11. The lead-free and antimony-free brass alloy according to claim 1, which further comprises from 40 to 42.5% Zn. 